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ID Date Authorup Type Category Subject
  14797   Mon Jul 22 13:26:41 2019 KruthiUpdateIOOMC locked

The MC2 has 2 GigE cameras right now. I'll put back the analog asap.


I found the MC2 face camera disabled(?) and the MC servo board input turned off. I turned the MC locking back on but I don't see any camera image yet.

  14798   Mon Jul 22 13:32:55 2019 KruthiUpdateSUSTest mass pitch adjustment test

[Kruthi, Milind]

On Friday, Milind and I performed the pitch adjustment test Rana had asked us to do. Only 1 blue beam in case of ITMX and two in case of ETMY, ETMX and ITMY were accessible. Milind (of mass 72 kg as of 10 May 2019) stood on each of the accessible blue beams of the test mass chambers for one minute and I recorded the corresponding gps time. Before moving to the next beam, we spared more than a minute for relaxation after the standing end time. Following are the recorded gps times. 







Beam 1

Beam 2

Beam 1

Beam 1

Beam 2

Beam 1

Beam 2

Standing start time (gps)








Standing end time (gps)








PS: For each blue beam relaxation time ~ 1 min after the standing end time

Attachment 1: ETMX.pdf
Attachment 2: itmx.pdf
Attachment 3: ETMY.pdf
Attachment 4: ITMY.pdf
Attachment 5: 3f1a82f2-b86a-469e-8914-9278a216c5f9.jpg
Attachment 6: 1d174307-d940-42e6-812b-83417d0f5f6a.jpg
  14803   Wed Jul 24 02:06:05 2019 KruthiUpdateCamerasHDR images

I have been trying a couple of HDR algorithms, all of them seem to give very different results. I don't know how suitable these algorithms are for our purpose, because they are more concerned with final display. I'm attaching the HDR image I got by modifying Jigyasa's code a bit (this image has been be modified further to make it suitable for displaying). Here, I'm trying compare the plots of images that look similar. The HDR image has a dynamic ratio of 700:1

PS: 300us_image.png file actually looks very similar to HDR image on my laptop (might be an issue with elog editor?). So I'm attaching its .tiff version also to avoid any confusion.

Attachment 1: HDR_8bit.png
Attachment 2: hdrplot.png
Attachment 3: C_MC2_2019-07-19-01-50-09.tiff
Attachment 4: 300us_image.png
Attachment 5: 300us_image.tiff
Attachment 6: actualimageplot.png
  14804   Wed Jul 24 04:20:35 2019 KruthiUpdateCalibration-RepairMC2 pitch and yaw calibration

Summary:  I calibrated MC2 pitch and yaw offsets to spot position in mm. Here's what I did:

  1. Changed the MC2 pitch and yaw offset values using  ezca.Ezca().write('IOO-MC2_TRANS_PIT_OFFSET', <pitch offset value> ) and ezca.Ezca().write('IOO-MC2_TRANS_YAW_OFFSET', <yaw offset value> )
  2. Waited for ~ 700-800 sec for system to adjust to the assigned values
  3. Took snapshots with the 2 GigEs I had installed - zoomed in and zoomed out. (I'll be using these to make a scatter loss map, verify the calibration results, etc)
  4. Ran the mcassDecenter script, which can be found in /scripts/ASS/MC. This enters the spot position in mm in the specified text file.

Results:  In the pitch/yaw vs pitch_offset/yaw_offset graph attached,

  • intercept_pitch = 6.63 (in mm) ,  slope_pitch = -0.6055 (mm/counts) 
  • intercept_yaw = -4.12 (in mm) ,  slope_yaw = 4.958 (mm/counts) 
Attachment 1: Pitchyaw_calibration.png
  14824   Fri Aug 2 16:46:09 2019 KruthiUpdateCamerasClean up

I've put the analog camera back and disconnected the 151 unit GigE. But I ran out of time and wasn't able to replace the beamsplitter. I've put all the equipments back to the place where I took them from. The chopper and beam dump mount, that Koji had got me for the scatterometer, are kept outside, on the table I was working on earlier, in the control room. The camera lenses, additional GigEs, wedge beamsplitter, 1050nm LED and all related equipments are kept in the GigE box. This box was put back into CCD cameras' cabinet near the X arm.

Note: To clean stuff up, I had entered the lab around 9.30pm on Monday. This might have affected Yehonathan's loss measurement readings (until then around 57 readings had been recorded).

Sorry for the late update.

  10829   Mon Dec 22 15:46:58 2014 KurosawaSummaryIOOSeven transfer functions

IMC OL TF has been measured from 10K to 10M

Attachment 1: MC_OLTF.pdf
  3235   Fri Jul 16 13:05:48 2010 Kyung-haUpdateSUSLate update for 7/13 Tue (Tip Tilts)

[Jenne & Kyung-ha]

We suspended the mirror to one of the main frame with the ECD backplane we finished before. The hard task was to find the right balance for the mirror so that 1) it won't be tilted and 2) it'll be in the right position for the ECD backplanes so that the magnets attached to the mirror holder would be in the very center of each ECD holes. We used optical lever laser (red He/Ne) to check the balance of the mirror. We tried to use the jig for the mirror holder clamps but because of the size difference, we couldn't use it at all. (Since the magnets are very heavy, we thought the wire being not perfectly centered might work better. However, the jig dimension was way too different that the wire ended up in the middle of one of the holes.) Since there was no other clever way to attach the wire in the right position, we just tried to be as center/accurate as possible. After attaching wire to that mirror holder clamps, we hanged it to the frame. Again, we couldn't find any other accurate way to find the center so we held the wire and tried to adjust the mirror height as accurate as possible so that it can be in the right position in respect to ECD backplane and not be tilted at the same time. However, when we hanged the mirror, it was still tilted.. So we adjusted the mirror tilt using the mirror holder clamps. Since the holes on the clamps were ellipse shapes, we could adjust the position of the clamps a little bit. When we adjust the clamps, we started to tighten the screws when the mirror is NOT in the perfect position since the tightening up part changes the mirror angle anyways. Luckily, when we tightened up the last screw, the mirror was in the perfect position! After that, we poked the mirror several times to make sure that it comes back to the same place.

Amazingly, we could finish this whole hanging/adjusting process in about 30 mins! :D (Jan said it's because of his amazing moral support. :P Maybe he'll be there to support us everytime we work on the mirrors?)

  6383   Wed Mar 7 23:28:41 2012 Lab Cleanup CrewHowToEnvironmentTrue Beauty....

Or, how a lab should look at the end of every day.


Beat that, Bridge kids!

  4307   Wed Feb 16 10:35:40 2011 Larisa ThorneUpdateIOOWFS quantum efficiency as a function of angle

 Here is the followup on Jenne's February 14th, 2011 update on the quantum efficiency measurements of WFS2.



Attached is a PDF of my calculations, based on measurements ranging between 0-25 degrees in 5 degree increments.

The graph at the bottom plots these angles versus the calculated quantum efficiency at each point and the responsivity. Since quantum efficiency and responsivity only differ by a factor of some natural constants (lamda, e, h, c), I used a graph with two vertical axes, because the points would be plotted at essentially the same location if quantum efficiency (%)  and responsivity (Amps/Watts) were graphed on two separate plots.

The calculated values for quantum efficiency based on my measurements (labelled "ExpAverage") were pretty close to what Jenne had calculated in earlier attempts, which was around 60%. Just to test, I compared my quantum efficiency result against the calculation of quantum efficiency using the responsivity value for silicon, 0.5 Amps/Watt, which is labelled as "Spec". Comparison of "ExpAverage" and "Spec" shows that they differ by only about 2%, so I conclude that the theoretical quantum efficiency calculated using a given responsivity agrees with my measurement-based experimental result.

Attachment 1: QEcalcs.pdf
  4346   Wed Feb 23 16:56:17 2011 Larisa ThorneUpdateVIDEOCable laying...continued

Having finished labeling the existing cables to match their new names, we (Steve, Kiwamu and Larisa) moved on to start laying new cables and labeling them according to the list.


Newly laid cables include: ETMXT (235'), ETMX (235'), POP (110') and MC2 (105').  All were checked by connecting a camera to a monitor and checking the clarity of the resulting image. Note that these cables were only laid, so they are not plugged in.


The MC2 cable needs to be ~10' longer; it won't reach to where it's supposed to. It is currently still in its place. 

The three other cables were all a lot longer than necessary.

  4358   Fri Feb 25 14:35:06 2011 Larisa ThorneUpdateElectronicsTotal harmonic distortion results for +7dBm mixer

 This experiment deals with measuring the total harmonic distortion (THD) contribution of mixers in a circuit.

(a circuit diagram is attached) where:

Mixer: ZFM-3-S+ at +7dBm

Attenuator: VAT-7+, at +7dB

Low-pass filter: SLP-1.9+, which is set to DC-1.9MHz


The total harmonic distortion can be calculated by the equation: 

\mbox{THD} =  \frac{V_2^2 + V_3^2 + V_4^2 + \cdots + V_\infty^2}{V_1^2}

where Vn represents the voltage of the signal at a certain harmonic n.


In this experiment, only the voltages of the first three harmonics were measured, with the first harmonic at 400Hz, the second at 800Hz, and the third at 1.2kHz. The corresponding voltages were read off the spectrum analyzer after it had time averaged 16 measurements. (picture of the general shape of the spectrum analyzer output is attached)

(results for this mixer's particular configuration are on the pdf attached)


There really isn't that much correlation between the modulations and the resulting THD.

We won't know how good these numbers are until more experiments on other mixers are done, so they can be compared. Since the rest of the mixers are relatively high levels (+17dBm, +23dBm in comparison to this experiment's +7dBm), an RF amplifier will need to be hooked up first to do any further measurements.






Attachment 1: THDcircuit.jpg
Attachment 2: Photo_on_2011-01-17_at_12.25.png
Attachment 3: THDwithoutamp.pdf
  4374   Thu Mar 3 18:32:33 2011 Larisa ThorneUpdateElectronicsHarmonic distortion calculations for RF distribution box

Finished calculations for harmonic distortion at each of the 10 outputs of the RF distribution box. The diagram can be found on Suresh's post  http://nodus.ligo.caltech.edu:8080/40m/4342


THD calculation consisted of gather data on the dBm at harmonics of the fundamental frequency. These dBm values were converted into units of power and plugged into the appropriate THD equation pulled from Wikipedia: 
\mbox{THD} = \frac{P_2 + P_3 + P_4 + \cdots + P_\infty}{P_1} = \frac{\displaystyle\sum_{n=2}^\infty P_n}{P_1}

On the table, the number 1-6 correspond to the harmonic number of the input frequency used. For example, the first five PD's listed used an 11MHz source, while the second set of five PD's listed used a 55MHz source. Values listed under certain harmonics are dBm measurements at the corresponding frequency. The P-subscript values are essentially the dBm measurements converted to units of power (Watts) for ease of calculation in the equation above. THD is then calculated using these power units; I have converted the ratios to percentages.


It should be noted that as with all THD calculations, the more data points collected, the more precise the THD % will be.

By the way, the outputs on the physical RF distribution box for REFL165 and AS165 are actually labeled as REFL166 and AS166. 

Attachment 1: RFdistribboxcalcs.pdf
  4402   Thu Mar 10 17:03:48 2011 Larisa ThorneConfigurationElectronicscalculations for passive low pass filter on X arm

[Kiwamu, Larisa] 


We want to increase gain in the lower frequencies, so a circuit must be designed (a passive low pass filter). 


First, measurements were taken at the X arm for impedance and capacitance, which were 104.5kOhms and 84.7pF respectively. Kiwamu decided to make the circuit resemble a voltage divider for ease of calculation, such that Vout/Vin would be a ratio of some values of the equivalent circuit reactance values. After a few algebra mistakes, this Vout/Vin value was simplified in terms of the R, C measured and the R', C' that would be needed to complete the circuit. 

Since the measured C was very small and the measure R was fairly high, the simplified form allowed us to pick values of R' and C' that would make the critical frequency occur at 0.1Hz: set the R' resistance to 1MOhm and C' capacitance to 10uF, which would yield a gain ~1.

With these values a circuit we can start actually making the circuit.

  4434   Wed Mar 23 16:06:20 2011 Larisa ThorneUpdateElectronicsUpdate on cable laying

 [Steve, Suresh, Larisa]

The following cables were laid today: ETMYT, ETMY, IFOPO, MC1, OMCR, AS Spare, and MC2T.


Though the paper suggested 135' for the MC2T, we used a 110'. This is too short: need at least another 15' for the MC2T.

The RCR cable wasn't crossed off on the list, but a cable exists at the RCR cable which is black and is labeled (old label, 75 ohms)

There was no indication of which length was needed for MC1, so a 95' cable was used.

  4456   Tue Mar 29 15:01:58 2011 Larisa ThorneUpdateElectronicsLow pass filter for X arm laser temperature control

 This is the continuation of http://nodus.ligo.caltech.edu:8080/40m/4402


The first picture is of the actual component, where the resistor is 1M and capacitor is 10uF. 

But before the component can be put into place, its transfer function had to be checked to make sure it was doing what we calculated it would do. The results of these are in the graphs generated: frequency vs. gain, and frequency vs. phase.




According to these graphs, we are not achieving the targeted cutoff frequency: need to recalculate and compensate for the extra 100k resistance being encountered.

Attachment 1: DSC_2889.JPG
Attachment 2: LPFgraph.pdf
LPFgraph.pdf LPFgraph.pdf LPFgraph.pdf LPFgraph.pdf
  4462   Wed Mar 30 17:01:08 2011 Larisa ThorneUpdateVIDEOCable laying...continued

[Steve, Suresh, Kiwamu, Larisa]


Only the PRM/BS cable was laid today.

In one of the previous updates on cable laying, it was noted that the MC2 cable needed an additional 10' and the MC2T needed an additional 15' to reach their destinations.  We cut and put BNC ends on 10' and 15' cables and connected them to the original cables in order to make them long enough.


This concludes the laying of new cables. Suresh is currently working on the QUADs...

  4492   Wed Apr 6 16:02:07 2011 Larisa ThorneUpdateElectronicsCable laying...continued

[Steve, Kiwamu, Larisa]


Having finished laying new cable last week, we moved on to connecting those on PSL table and AP table.

Cables connected:

--RCR, RCT, PMCR (all three are blue)

--OMCR (blue cable, ***now has a camera***), PMCT, IMCR, REFL, AS (white cable), OMCT (***now has camera***)


Unless otherwise noted, the cables are black on the AP table. Also on the AP table: cables were connected directly to the power source.

The wiki has been updated accordingly.


Steve noted that MC2T and POP cameras are not there.



  4519   Wed Apr 13 16:38:17 2011 Larisa ThorneUpdateElectronicsVideo MUX camera/monitor check

 [Kiwamu, Larisa]


The following Video MUX inputs(cameras) and outputs(monitors) have been checked:

MC2F, FI, AS Spare, ITMYF, ITMXF, ETMYF, ETMXF, PSL Spare, ETMXT, MC2T, POP, MC1F/MC3F, SRMF, ETMYT, PRM/BS, CRT1(MON1), ETMY Monitor, CRT2(MON2), CRT4(MON4), MC1 Monitor, CRT3(MON3), PSL1 Monitor, PSL2 Monitor, CRT6(MON6), CRT5(MON5), ETMX Monitor, MC2 Monitor, CRT9, CRT7(MON7), CRT10, and Projector.


Their respective statuses have been updated on the wiki:   (wiki is down at the moment, I will come back and add the link when it's back up)

  4531   Fri Apr 15 13:40:00 2011 Larisa ThorneUpdateElectronicsLow pass filter for X arm laser temperature control, second try

Plotting the data points yielded by the spec analyzer of my first LPF yielded a result that was not expected: the desired cutoff frequency wasn't achieved because of some extra 100k resistance that wasn't taken into consideration. (see  here ). I have redrawn the Bode graphs for this configuration so that it is easier to see that it is wrong (first attachment)


After some calculation adjustments, it was found that the capacitor value could remain at 10uF, but the resistance needed to be changed to 100k to maintain a gain of 0.5 and critical frequency at 0.1Hz. Second attachment is the Bode graph that results from this configuration.


Note: Bode graphs are both in Log-Linear scales (Wikipedia said so)


Attachment 1: Bode2.jpeg
Attachment 2: Bode100k.jpg
  4612   Tue May 3 14:35:44 2011 Larisa ThorneConfigurationElectronicsJenne-Seismometer LPF project

 I was charge with making a Non-Inverting Op Amp Low Pass Feedback circuit for Jenne, which may somehow be integrated into a seismometer project she's working on.


Circuit diagram is attached. Calculations show that R1, R2 and C have the following relationship: if R1=10^n, R2=10^(n+1), C=10^(-n-4). For the particular circuit being modeled by the transfer function, R1=100 Ohm, R2=1k Ohm, and C=1uF.

Attached also is the circuit's Bode plot, showing frequency versus gain and phase, respectively. The frequency versus gain graph is true to what the circuit was calculated to generate: a gain of +20 and a cutoff frequency at 200Hz. Not sure what's going on with the frequency verus phase plot.

Attachment 1: SeisLPFdiagram.jpg
Attachment 2: seisLPF.Bose.jpg
  4614   Tue May 3 15:48:26 2011 Larisa ThorneUpdateElectronicslaser temperature control LPF, final version!

This is a continuation of this

 The low pass filter is finally acceptable, and its Bode graph is below (on a ~3Hz frequency span that shows the cutoff frequency is at 0.1Hz)

Attachment 1: LPF100k.2.jpg
  4630   Wed May 4 17:32:06 2011 Larisa ThorneConfigurationElectronicsJenne-Seismometer LPF project

Building on what was posted previously



The configuration has now evolved into an Inverting Op Amp Feedback Low Pass Filter circuit.

Had to change out some components to satisfy conditions: R1=1k Ohm, R2=10k Ohm, C=0.1uF. These were changed in order to decrease the magnitude of the current passing through the op amp by a factor of 10 (10V supplied through the R1 resistor yields about 10mA). The configuration itself was changed from non-inverting to inverting in order to get the frequency vs. gain part of the Bode plot to continue to decrease across higher frequencies instead of leveling off around 4kHz.

Attachment 1: SeisLPF3.jpg
  4634   Thu May 5 12:01:53 2011 Larisa ThorneConfigurationElectronicsJenne-Seismometer LPF project

 Having finished the bulk of the work for the LPF itself ( see here ), I have begun trying to design the seismometer box to Jenne's specifications.


Currently looking into what the voltage buffer amplifier might look like for this.



Suggestions/corrections would be much appreciated!



Attachment 1: STS2diagram.png
  4690   Wed May 11 16:04:36 2011 Larisa ThorneConfigurationElectronicsJenne-Seismometer LPF project

The schematic for the seismometer box from this last time  has been updated...


Koji was helpful for coming up with a general diagram for the voltage buffer amplifier, which has now been added to the configuration pictured below.

The only thing that remains now before I try to plot it with Eagle/LISO is to pick an op amp to use for the voltage buffer itself. Someone suggested THS4131 for that (upon Googling, it hit as a "high speed, low noise, fully-differential I/O amplifier"). It looks good, but is it the best option?

Attachment 1: STS2diagram2.png
  4774   Tue May 31 16:07:57 2011 Larisa ThorneConfigurationElectronicsSeismometer Box Update

 (Continuation of this)


I plugged the circuit into the LISO program to generate the graphs below....the first graph is a plot of frequency (f, in Hz) versus gain (in dB), and frequency (f, Hz) versus phase (in degrees). Also included is the second graph, which is a noise plot of all circuit parts which contribute to the total noise of the circuit.


The only issue I had was that two of the op amps I'd picked (see third attachment for the original circuit diagram) for the circuit were not in LISO's op amp library. So I replaced THS4131 (from the voltage buffer part) and AD826 (from the ADC driver part) with AD797 and LT1037, respectively in order to generate the plots below....   


There are notes calling the AD797 "ultra low noise, low distortion", whose data sheet can be found here: AD797 

Notes also call LT1037 "low noise, high speed precision op amp", whose data sheet can be found here: LT1037


I've put these in temporarily only, as I don't know if they are appropriate choices for the job or even if we have them. Suggestions?

Attachment 1: SeisBoxLISOplot1.pdf
Attachment 2: SeisBoxLISOplot2.pdf
Attachment 3: STS2diagram_original.pdf
  4785   Sat Jun 4 15:26:04 2011 Larisa ThorneUpdateElectronicsSeismometer Box Update

 (continuation of this)


Here are the transfer function and noise plots of the seismometer box, using the op amps that are actually indicated on the original plan (THS4131, AD826). I added them to the LISO op amp library (can be found in /cvs/cds/caltech/apps/linux64/liso/filter/opamp.lib)

Next step is to compare the noise graph below to the seismic noise curve of the interferometer to verify that the seismometer box configuration won't affect the curve...

Attachment 1: SeisBoxLISO_transfer.pdf
Attachment 2: SeisBoxLISO_noise.pdf
  4807   Fri Jun 10 20:23:56 2011 Larisa ThorneUpdateElectronicsSeismometer Box Update/graphs

 (continuation of this)


The noise graphs relating total noise of the Seismometer circuit (GURALP stuff) to the LIGO seismic noise curve have been completed started.



I apparently harbor hate towards Matlab (you may have notice I do everything in Mathematica)....I will try to change my ways  DX

Attachment 1: SeisNoiseGraphs.jpg
  4998   Wed Jul 20 11:13:59 2011 Larisa ThorneUpdateelogI restarted the ELOG as it seemed to have crashed


  10473   Mon Sep 8 16:23:25 2014 LarryHowToComputer Scripts / Programsaccessing 40m data remotely with python


Attached is an example script showing how to access 40m data remotely. The only two nonstandard python modules you need are the nds2 client module and astropy (used for time conversion). For mac users, both of these are available via macports (nds2-client and, e.g. py27-astropy). Otherwise, check out their websites:




Have fun!



Attachment 1: get40mData.ipynb.gz
  13683   Thu Mar 15 16:00:25 2018 Larry WallaceSummaryComputersCert renewal for NODUS

The cert for nodus has been renewed for another 2 years.

The following is the basic procedure for getting a new cert: (Note certs are only good for two years as of 2018)
openssl req -sha256 -nodes -newkey rsa:2048 -keyout nodus.ligo.caltech.edu.key -out nodus.ligo.caltech.edu.csr
Country Name (2 letter code) [AU]:US
State or Province Name (full name) [Some-State]:CaliforniaLocality Name (eg, city) []:Pasadena
Organization Name (eg, company) [Internet Widgits Pty Ltd]:California Institute of Technology
Organizational Unit Name (eg, section) []:LIGO
Common Name (eg, YOUR name) []:nodus.ligo.caltech.edu

Leave the e-mail address, challenge password and optional company name blank. A new private key will be generated.
chown root nodus.ligo.caltech.edu.key
chgrp root nodus.ligo.caltech.edu.key
chmod 0600 nodus.ligo.caltech.edu.key

The nodus.ligo.caltech.edu.csr file is what is sent in for the cert.
This file should be sent to either ryan@ligo.caltech.edu or security@caltech.edu and copy wallace_l@ligo.caltech.edu.

A URL llink with the new cert to be downloaded will be sent to the requestor.

Once the files are downloaded, the new cert and intermediate cert, they can be copied and renamed.

The PEM-encoded host certificate by itself is saved at:


The nodus.ligo.caltech.edu.key file should be in the same directory or whichever directory is indicated in the ssl.conf located in /etc/httpd/conf.d/  directory.

httpd will need to be restarted in order for it to see the new cert.


  15201   Mon Feb 10 09:40:54 2020 Larry WallaceSummaryGeneralSolidWorks Computer Upgrade and Printer repair

On February 5, 2020, the Dell engineering workstation located in the 40M lab, was replaced with a newer Engineering workstation, per a request from Koji . The new workstation should perform a good deal better over the older unit. It has more cores, more memory and a better video card. Since this unit is being used by the 40M group, the Comsol s/w pkg. was also installed on the unit.

During the computer swap, Koji had a problem with a print job and it was discovered the bottom tray of the HP5550 printer was broken. The broken tray was replaced from another unit that was being disposed of.

  15274   Fri Mar 13 12:48:47 2020 Larry WallaceUpdateelogCert Renewal

Updated the cert in /etc/httpd/ssl. The new cert is good until March 12, 2022.

  4611   Tue May 3 13:22:13 2011 LeoUpdateSUSRe: DRMI prep : suspension diagnostic

Here are the free-swinging spectra for the BS, ETMX, ETMY, ITMX, ITMY, MC1, MC2, MC3, and PRM chambers.  Kiwamu left the suspensions free for 5 hours this weekend, starting at Sat Apr 30 00:15:26 2011.

This is GPS time 988 182 941.  Quick tip: you can do local to GPS time conversions using lalapps_tconvert, which is a lot like tconvert but with special powers.  It is installed on pianosa.

$ lalapps_tconvert Sat Apr 30 00:15:26 2011


I generated these figures with the attached Python script, measure.py.

Notice that the C1:SUS-ITMX_SENSOR_UL and C1:SUS-MC3_SENSOR_UL spectra fall as 1/f.  Jenne suggested that this might indicate that there is a loose electrical connection.

Also, notice that C1:SUS-ETMY_SENSOR_LR, C1:SUS-ITMY_SENSOR_LL, and C1:SUS-PRM_SENSOR_SIDE are a lot noisier above 10 Hz.

Attachment 1: BS.png
Attachment 2: ETMX.png
Attachment 3: ETMY.png
Attachment 4: ITMX.png
Attachment 5: ITMY.png
Attachment 6: MC1.png
Attachment 7: MC2.png
Attachment 8: MC3.png
Attachment 9: PRM.png
Attachment 10: SRM.png
  3643   Mon Oct 4 13:48:41 2010 Leo SingerConfigurationComputersUninstalled gstreamer-devel and gstreamer-plugins-base-devel on rosalba

 I uninstalled gstreamer-devel and gst-plugins-base-devel on Rosalba.  Here is the command I ran:

$ sudo yum remove gstreamer-devel gstreamer-plugins-base-devel


Actually, I had installed these myself a few days earlier, before I knew that I should be recording such changes in the elog.  I'm sorry!

  3650   Tue Oct 5 13:59:17 2010 Leo SingerConfigurationComputersInstalled x264-devel on Allegra

 I installed the package x264-devel on allegra.martian.  This package provides headers and libraries for the popular h264 video codec.  I am going to use this in the GStreamer streaming media server on Allegra.

  3718   Thu Oct 14 13:09:01 2010 Leo SingerConfigurationComputersnds2-client-devel installed on rossa

I installed nds2-client-devel on rossa using the following command:

$ sudo yum install nds2-client-devel

  3719   Thu Oct 14 13:15:14 2010 Leo SingerConfigurationComputersgit installed on rossa

I installed git on rossa using:

$ sudo yum install git

  3721   Thu Oct 14 14:52:52 2010 Leo SingerConfigurationComputersnumpy, ipython, matplotlib, python-matplotlib installed on rossa

I installed the following packages on rossa:

numpy, ipython, matplotlib, python-matplotlib

  3835   Mon Nov 1 12:38:56 2010 Leo SingerConfigurationComputerspython-sqlite installed on Allegra

I installed the Python bindings for sqlite on Allegra using

$ sudo yum install python-sqlite python-sqlite2

  3990   Mon Nov 29 18:05:17 2010 Leo SingerConfigurationComputersinstalled graphviz on Rosalba

I installed the following packages on Graphviz in order to support visualization of GStreamer pipeline graphs:


  4642   Thu May 5 15:26:52 2011 Leo SingerConfigurationComputers'glue' installed on some control room computers

I installed 'glue' on Rossa, Allegra, and Rosalba.  This is a Python module that includes a facility for LIGO_LW XML files.  Oddly, I couldn't find the glue package on Pianosa.

  4646   Thu May 5 17:19:21 2011 Leo SingerConfigurationSUSTuning notch filters for bounce mode suspensions

I am tuning the notch filters for the bounce modes in the suspensions, starting with the ITMs and ETMs.  I'll do the MCs, the PRMs, and the SRMs next.


I noticed that the filter for ITMX (in the file C1SUS.txt, the module ITMX_SUSPOS, the selection BounceRoll) that the filter was composed of two bandstops (and a constant gain).  It looked like this:




Valera said that one of these was for the roll mode and the other for the bounce mode.  However, looking at the spectra that Kiwamu and I made this week, I don't perceive a resonance between 11.4 and 12.2 Hz.  So, we're taking a guess that this was for a mode that has moved due to new pendulum designs.  For many of the suspensions, in the free swinging test we noticed a line around 23 Hz; we thought we might as well re-use one of these elliptical filters to avoid exciting this line.  Of course, if this line does *not* result from excitation of an uncontrolled degree of freedom, this will not help and could be detrimental.  When we talk to Valera again, we can review this decision and at that point we might decide just to take out that bandstop.


ITMX is done.  I'll continue tomorrow.  I've attached closed-loop spectra for before the tuning (itmx-before.pdf) and after (itmx-after.pdf).


(Update: the following day, I took closed loop spectra with (itmx-withbounceroll.pdf) and without (itmx-nobounceroll.pdf) the bandstops.  It looks like the bandstops made the bounce mode slightly worse, but the roll mode slightly better.)



Attachment 1: itmx-before.pdf
Attachment 2: itmx-before.pdf
Attachment 3: itmx-withbounceroll.pdf
Attachment 4: timx-nobounceroll.pdf
  4652   Fri May 6 14:59:36 2011 Leo SingerConfigurationSUSTuning ITMY bandstop

I tuned the ITMY bandstops -- 'before' and 'after' spectra attached.  Note that the after the tuning, the bounce mode at ~16 Hz is about twice as quiet!


However, notice that in the 'before' plot the roll mode at about 23.5 Hz did not show up at all, whereas it is quite prominent in the 'after' plot.  I was concerned that this line could have been a result of placing the bandstop there, so I made another plot with the BounceRoll filter turned off.  Sure enough, the 23.5 Hz line is still there.  So I'm not crazy: the roll mode did start acting up at some time between my 'before' and 'after' plot, but not as a result of the tuning.

Attachment 1: itmy-before.pdf
Attachment 2: itmy-after.pdf
Attachment 3: itmy-nobounceroll.pdf
  4712   Fri May 13 14:54:20 2011 Leo SingerUpdateComputersDiaggui fixed on pianosa

I fixed diaggui on pianosa.  Previously, it was not able to start because it depended on libreadline5, whereas Ubuntu distributed libreadline6.  Now pianosa has both libreadline5 and libreadline6, so diaggui works.

  4713   Fri May 13 17:20:48 2011 Leo SingerConfigurationSUSTuned bounce and roll mode of ETMY suspension

I tuned the bounce and roll mode bandstops for ETMY, although it was difficult for me to tell if there was improvement with the bandstops on relative to the bandstops off because it seemed like the bounce and roll modes were being excited intermittently.  I'll take spectra with the filters both on and off during an evening next week.

  6105   Mon Dec 12 11:34:40 2011 Leo SingerSummaryGeneralSome design parameters for a Stewart platform

At the suggestion of Rana and Koji, I have worked out some design parameters for a Stewart platform to be used as a vibration isolation device or as a platform for characterization of suspensions.  I have made some initial guesses about the following design requirements:

  • linear travel: 40 microns peak to peak (based on SOS design requirements in LIGO-T950011)
  • angular travel: 3 mrad peak to peak (based on SOS design requirements in LIGO-T950011)
  • payload mass: 5 kg (wild guess of mass of loaded SOS)
  • payload moment of inertia: 0.01 kg m^2 (wild guess)
  • bandwidth: 500 Hz (suggestion of Rana and Koji: ~kHz)

From these assumptions, I have worked out:

  • peak actuator force: 0.88 kN
  • minimum radius of top platform: 15 cm
  • minimum radius of bottom platform: 30 cm
  • minimum height: 26 cm

The combination of high force, high speed, and ~micron travel limits seems to point to piezoelectric actuators.  PI's model P-225.80 would meet the peak push-pull force requirement, but I have not yet determined if it would meet the bandwidth requirement.  Apparently, typical piezoelectric actuators can exert a greater push force than pull force; wonder if one could use an actuator with a smaller force range than the P-225.80 if the actuator is biased by compression.  (Is this what is meant by a "preloaded" actuator?) 

I have attached a PDF explaining how I worked out the actuator force and platform dimensions.  (I'll try to dice up this PDF and put the contents in the Wiki.)  I also have a plant model in MATLAB with which I have been playing around with control schemes, but I don't think that this is ready to show yet.

Here are some tasks that still remain to be done for this preliminary case study:

  • select sensing technologies: integrated linear encoders and/or strain meters, inertial sensing, optical levers, etc.
  • study joints: Koji and Rana suggest flexures; I need to propose the joint geometry and material
  • study internal modes of the platforms and actuators themselves
  • build noise budget

I'd like to ask for input principally on:

  • appropriateness of my design assumptions
  • piezo actuators currently in use in the lab

 Edit: I also added a Mathematica notebook with the inverse kinematics (mapping from platform state to leg lengths) of the platform. 






Attachment 1: stewart.pdf
stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf stewart.pdf
Attachment 2: stewart.nb
(* Content-type: application/vnd.wolfram.mathematica *)

(*** Wolfram Notebook File ***)
(* http://www.wolfram.com/nb *)

(* CreatedBy='Mathematica 8.0' *)

(*CacheID: 234*)
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  6163   Tue Jan 3 20:42:05 2012 Leo SingerUpdateGeneralActuators for Stewart platform

 I checked on the two single-axis shakers that are present at the 40m that Steve pointed out:

  • Brüel & Kjær type 4809, rated for 45 N peak, and
  • Brüel & Kjær type 4810, rated for 10 N peak.

Neither of these meet the force requirement of 2.04 kN peak.

  6185   Wed Jan 11 14:06:28 2012 Leo SingerHowToComputer Scripts / ProgramsHowTo for getting data from NDS off site

 This may or may not be general knowledge already, but Jamie and I added a HowTo explaining how to retrieve channel data from the frame builder via NDS, but off site on one's own computer.  See the Wiki page:


  6191   Thu Jan 12 11:08:23 2012 Leo SingerUpdatePEMFunky spectrum from STS-2

I am trying to stitch together spectra from seismometers and accelerometers to produce a ground motion spectrum from Hz to 100's of Hz.  I was able to retrieve data from two seismometers, GUR1 and STS_1, but not from any of the accelerometers.  The GUR1 spectrum is qualitatively similar to other plots that I have seen, but the STS_1 spectrum looks strange: the X axis spectrum is falling off as ~1/f, but the Y and Z spectra are pretty flat.  All three axes have a few lines that they may share in common and that they may share with GUR1.

See attached plot.

Attachment 1: spectrum.jpg
  6192   Thu Jan 12 21:22:16 2012 Leo SingerConfigurationWIKI-40M UpdateUnable to create Wiki page

 I can't create a new page on the 40m wiki.  The page that I was trying to create is


I get this message when I try to save the new page:

Page could not get locked. Unexpected error (errno=13).

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